1. Field of the Invention
The present invention relates to a flat display device and, more particularly, to a flat display device used as an image display for use in computer, television, and the like.
2. Description of the Prior Art
The plasma display panel (referred to as PDP hereinafter) as a flat display device has been put into practical use of a display device such as a wall hanging television set. PDPs are classified into AC type and DC type according to difference in voltage drive system. In most cases, a display portion of an AC type color PDP has a structure shown in FIG. 1, for example.
In FIG. 1, address electrodes 102 and a fluorescent layer for covering these address electrodes 102 are formed on a back glass substrate 101. A dielectric layer 105, a pair of display electrodes 106, 107, a protection layer 108, etc. are formed on a front glass substrate 104 opposing to the back glass substrate 101. In addition, a gas is sealed into a discharge space 109 between the front glass substrate 104 and the back glass substrate 101.
In practical use of such PDP, lifetime of the panel, operating voltage, emission luminance, chromatic purity and so on are to be considered as important evaluation factors. These evaluation factors are significantly affected by gas mixture which is sealed into the discharge space 109.
Various investigations about such gas mixture have been performed. By using two component gas mixture consisting of neon (Ne) and xenon (Xe), or helium (He) and xenon, otherwise three component gas mixture consisting of helium, argon (Ar) and xenon, or neon, argon and xenon, such PDPs having long lifetime, low operating voltage, and in addition sufficient luminous brightness are going to be achieved.
Lights having wavelength other than visible ray, e.g., near infrared rays are emitted from PDPs using such gas mixture.
Such facts have been made clear by the inventors of the present invention that there are possibilities that such near infrared rays cause a harmful influence on transmission of infrared data in the POS (point of sales) computer information system used in the location where PDP is established, or cause malfunction of near infrared remote control for domestic electric appliances in the home where PDP is used as the television set.
These facts have not been known until now, and they have been found at first by the inventors of the present invention.
The present invention has been made to solve such problems, and an object of the present invention is to provide a flat display device capable of cutting off unnecessary lights for image display and improving quality of image display.
According to the present invention, since the flat display device is provided with means for reflecting or absorbing at least near infrared rays in wavelength bandwidth other than visible rays, malfunction of the devices operated by near infrared rays can be prevented. In addition, if an optical film serving as an anti-reflection film with respect to visible ray wavelengths and serving as a reflection film with respect to near infrared wavelengths is used as means for reflecting or absorbing near infrared rays, visible rays can be emitted from the flat display device to the outside without reflection and absorption in the flat display device. For this reason, deterioration in luminous display brightness of the flat display device can be prevented.
Further, since the flat display device is provided with the electromagnetic wave shielding film as well as means for reflecting or absorbing near infrared rays, harmful influence upon a human body can be suppressed. The electromagnetic wave shielding film may be formed of a lamination film, or a growth film deposited in terms of sputtering, CVD, evaporation, and the like.
Furthermore, in the flat display device, if the protection plate including glass, acrylic resin, or plastic is arranged in front of the substrates which define the discharge space, radiation of the light having shorter wavelength than visible rays can be suppressed and also the structure of the device can be strengthened. If the protection plate is formed to have a convex shape or the periphery of the protection plate is fitted into the frame member, structural strength of the protection plate can be improved.
In the present invention, since xenon and neon are included in the gas discharge space in the flat display device such that xenon comprises a less than 2% of the total, the radiant quantity of the light emitted from the flat display device and having 800 nm to 1200 nm wavelength can be extremely reduced. Therefore, harmful influence of the flat display panel upon the devices operated by near infrared rays can be prevented. In addition, quality of color display near the flat display panel can be improved. In the flat display panel, since there is a possibility to increase the radiant quantity of the light around 700 nm, optical intensity at the wavelength can be reduced by providing means for absorbing or reflecting the light having the wavelength beyond 650 nm to suppress deterioration in chromatic purity and chromaticity of color display.
In this event, if transmittance of the light having the wavelength below 650 nm is set to more than twice as high as the transmittance of the light having the wavelength of 700 nm, optical intensity at the wavelength can be reduced to suppress deterioration in chromatic purity and chromaticity of color display.
In the present invention, if the mixture ratio of the gas is set such that the spectrum intensity of infrared rays is less than the half of spectrum intensity of visible ray wavelength in the gas discharge space of the flat display device, influence upon the devices other than the flat display device can be reduced.
Other and further objects and features of the present invention will become obvious upon an understanding of the illustrative embodiments about to be described in connection with the accompanying drawings or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employing of the invention in practice.